Brake-shoe



(No Model.)

W. D. SARGBNT.

BRAKE SHOE. 7 No. 426,072. Patented Apr. 22, 1890.

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UNITED STATES PATENT OFFICE.

YVILLIAM D. SARGENT, OF EVANSTON, ASSIGNOR TO THE OONGDON BRAKE SHOE COMPANY, OF CHICAGO, ILLINOIS.

SHOE.

SZPECIFIGATION formingpart of Letters Patent No. 426,072, dated April 22, 1890.

Application filed January 9, 1890.

To aZZ whom it may concern:

Be it known that 1, WILLIAM D. SARGENT,

a citizen of the United States, residing at Evanston, in the county of Cook and State of Illinois, have invented a certain new and useful Improvementin Brake-Shoes, of which the following is a description.

The object of my invention is to produce a brake -shoe the bearing surfaces of which [0 shall combine increased durability and density with the softness necessary to afford the proper frictional resistance under pressure.

It is generally agreed by the master carbuilders that the material best adapted to the production of brake-shoes is soft cast-iron, this material presenting the greatest possible frictional resistance under pressure combined with strength. lleretofore great trouble has been experienced in utilizing soft cast-iron for this purpose, because of the rapid destruction thereof by wearing away, it being found impossible to contribute material durability by resistance to abrasion. It has been endeavored to overcome this defect by making part of the surface of chilled sections; but this has been found unsatisfactory.

My invention overcomes the objection to the use of soft cast-iron, and produces a brakeshoe having much greater durability combined with the softness of one made of sand cast iron. The method of manufacture is not here claimed, as it forms the subject of a separate application for Letters Patent.

My improvement consists in giving to the brake-shoe in the process of casting, at the bearing-surface, to the thickness or depth of an inch, (more or less,) a greater density than the body of the casting without chilling and consequent hardening.

In the drawings, Figure 1 is a perspective View, and Fig. 2 a crosssection illustrating my brake-shoe, which for the purpose of illustration is shown as of the Ross pattern, so called.

A represents the brake-shoe, and. B that Serial No. 336,352. (No model.)

part thereof which is made denser, and which in the ordinary casting extends about one inch into the casting.

To produce this shoe, I use a mold of the kind used for making chilled brakeshoes, and coat the same with a protective coating of plumbago or blackwash. The mold is made of the desired thickness, which is varied in different parts, so as to present a greater or less resistance to the accession of heat, and I also use convenient means for regulating the relative temperature of the mold and molten metal. Ipour the molten metal upon the mold, coated as described, and allow it to set. The protective coating prevents that hardening of the cast metal observed in the ordinary chilling process and leaves the cast metal of the necessary soft character, while the condensation is very great for about an inch below the surface, more or less, according to the thickness of the mold. The product is a brakeshoe having its bearing-face to the depth of about one inch of very great density compared with the remainder of the casting, while it is so soft as to confer the best results as a friction-bearing.

The kind of iron to be used is immaterial, although it may be found necessary to vary the thickness of the mold with different kinds of metal.

What I claim as my invention, and desire to secure by Letters Patent, is

1. A brake-shoe made of soft cast-iron and having its bearing-surface to a reasonable depth made denser than.the balance of the 80 casting without chilling.

2. A brake-shoe having a bearing-surface of soft cast-iron of increased density without being chilled or hardened, substantially as described.

WM. D. SARGENT.

Witnesses:

BRUCE S. ELLIOTT, WM. J. LITTELL. 

